warner



Feb. 14, W D WARNER HYDRAULIC OVERSHOT 2 Sheets-Sheet l FIG. 2

FIG. 3

Filed March 19, 1952 INVENToR. W. D. WARNER ATTORNEY Feb. 14, 1956 w. D.WARNER HYDRAULIC ovERsHoT 2 Sheets-Sheet 2 Filed March 19, 1952 ATTORNEYUnited States Patent() HYDRAULIC OVERSHOT William D. Warner, OklahomaCity, Okla.

Application March 19, 1952,l Serial No. 277,380

9 Claims. (Cl. 294-86) This invention relates to improvements inovershots for removing stuck drill pipe from well bores and moreparticularly, but not by way of limitation, to an improved overshotadapted to be interposed in a string of wash pipe.-

' As it is well known, during the drilling of deep wells, thedrillingbit is frequently forced in a direction varying from thevertical by slanting formations and the like, resultingin a crooked wellbore. After the drilling bit has been forced from a vertical course andthen returns to a vertical course, the drill pipe positioned above thedrill bit frequently wears a small opening adjacent the well boreproper. As a result, when the drill bit is subsequently removed from thewell bore, the drill collars, positioned adjacent the drill bit andbeing of larger diameter and stiller than the drill pipe, are frequentlylodged in the narrow opening adajcent the well bore to prohibitcornplete removal of the drill bit. In such a situation, it is thennecessary tol cut the drill pipe a distance4 above the drill bit anddrill collars. A string of pipe usually called the wash pipe, and beingof larger diameter than the drill pipe, is then run into the well boreand telescoped over the upper end of the several drill pipe. Fluid isthen forced down through the wash pipe to wash loose the drill pipe anddrill collars to facilitate the removal thereof. As the drill pipe iswashed loose, it usually falls baci; down to theA bottom of the wellbore.

kAt the present time, the usual procedure is to remove the wash pipefrom thewell bore and run another string of pipe or tubing into the Wellborewith an overshot on the lower end thereof' for removing the fallendrill pipe and drill bit. It will be apparent that the removal of thewashy pipe and the insertion of another string of pipe into the wellbore entails considerable manhours and lengthens the time during whichthe well is being drilled.

The present invention contemplates a novel overshot adapted to beinterposed in the wash pipe and telescoped down over the stuck drillpipe during the washing operation. As the drill pipe is'washed loose andstarts to fall tothe bottom of the Well bore, the overshot engages oneof the tool joints remaining on the drill pipe to stop the fall ofy thedrill pipe and permit immediate removalthereof. The overshot contains amovable carrier therein which is adapted to move a short distance in theovershot proper during the initial fall of the drill pipe. The carrieris so constructed and arranged with respect to the overshot housing orbowl to provide a shock absorbing action for the carrier and the drillpipe. In this manner the shock resulting from stopping the fall of thedrill pipe is reducedv to a minimumand reduces the wear and tear on thewash pipe. It is contemplated to provide two types of overshots; one forengagingtool joints having ilat ends and one for engaging tool jointshaving tapered ends.

An important objectof this invention is to provide a novel overshot`adapted to be` interposed in a string of washpipe.

Anotherz objecty of,A this invention is tov reduce to a minimum thenumber of trips or runs of pipe into a well bore for the removal ofstuck drill pipe.

A further object of this invention is to catch drill pipe during itsfall subsequent to the washing loose of the drill pipe.

Another object of this invention is to provide an overshot wherein theshock of stoppin-g falling drill pipe is reduced to a minimum.

A still further object of this invention is to provide an overshothaving a movable carrier therein utilizing a hydraulic shock absorber tocontrol the movement of the carrier.

Another object of this invention is to provide an overshot which may bereadily disengaged. from a drill pipe in the event the drill pipe cannotbe removedfrom a well bore.

A further object of this invention is to provide anovershot having alongservice life and which may be economically manufactured.

Other objects and advantages of the invention will be evident from thefollowing detailed description, read in conjunction with theaccompanying drawings, which illus.- trate my invention. l

In the drawings:

Figure l is a vertical sectional view, partially in elcvation, of anovel overshot interposed in a string; of wash pipe with a string ofdrill pipe shown in dotted linesex-V tending through the overshot in anonfengaging relationship therewith..

Figure 2 isy ay detailed. crossl sectional View of they dogs utilized inthe overshot to engage the drill. pipe.

Figure 3 is an exploded View illustrating the assembly of the dogs.

Figure 4 is a vertical crossy sectional view of the overshot shown inFig. l showing the overshot engaged with a tool joint. v

Figure 5 is a vertical sectional view of a modied over,- shot forengaging tool joints having tapered ends.

Figure 6 is a perspective View of the. upper sectionv of the carrierutilizedA in. the overshot shown inFig. 5..

Figure 7 is a detailed View of. a. frictionshoe utilizedin the modifiedovershot shown in Fig. 5.

Figure 8 is a detailed cross sectionalview of slips utilized in theovershot shown-in Fig. 5. y

Referring to the drawings in detail, and particularly Figs. 11 andl 4,reference character 2` generally designates a novel overshot, forengaging tool. joints havingiiat ends and interposed in a string of washpipe 4;, The'overshot 2 comprises a cylindrical, housing 6constructedinv two sections 8 and l0.; The upper end 12. of theupperhousing sectionv 8 is threadedly connected to one section of thewash. pipe 4, and the lower end 14'of. the 'lowerhousing section 1i) isthreadedly connected through the` medie um of a coupling 16 to anothersectionof'the washzp'ipe 4. Therefore, the` overshot 2l is'simplyinterposeduin, kthe wash pipe 4 in axial alignmenty therewith. Thesections-8 and lll' of theV housing 6. are threadedly interconnected at18 (more clearly shown in Fig. 4) in such afmanner-tnat the upper end 20of the section l0 extends upwardly Into the section 8.

A bore 22,-comparable in diameterv to the inner diametery of the washpipe 4, extends longitudinally partially through the lower housingsection 1l); The bore 22 is enlarged in the central portion of theYsectionA 10to provide a circumferential' tapered shoulder 24. Thehousing 1'0.-is provided with an upper enlarged section 26incommunication with the bore 224 and extendingupwardly to one ofthe theupper end 20 of the section 10." A bore 28, al'so f comparable indiameter tothe'l inner diameter of the wash pipe 4, extendslongitudinally'partially' through tlieupper housingsection 8; Thebore.2i8 is enlarged ati 30'topro.- videa circumferential: tapered'shoulder slightly above the central portion of the upper section 8. Thehousing 8 is provided with a lower enlarged portion 32 in communicationwith the bore 28 and is greater in diameter than the enlarged bore 26 ofthe lower section 10 and is of a size to receive the upper end of thelower housing section 10.

A tubular shaped carrier 34 is reciprocally disposed in the bore 26 ofthe lower housing section 10. The carrier 34 is of a size to provide asliding t thereof in the bore 26 and is of a length to extend upwardlyinto the bore 32 of the upper housing section 8. A circumferentialflange 36 is provided on the upper end of the carrier 34 and is of asize to provide a sliding fit thereof in the bore 32. The ilange 36obviously reciprocates in the bore 32 upon vertical movement of thecarrier 34 in the bore 26. The annular space or chamber 38 providedbetween the carrier 34 and the walls of the bore 32, when the carrier 34is in an upper position as shown in Fig. l, is normally lled with ahydraulic fluid and preferably a heavy lubricant for purposes as willhereinafter appear.

A plurality of breakable studs 40 (only one of which is shown) arethreadedly secured in the upper section 8 of the housing 6 and extendinwardly into the bore 32. The studs 40 are normally disposed below theflange 36 to retain the carrier 34 in its uppermost position as shown inFig. 1. However, the studs 40 may be broken when a force is imposed uponthe upper end of the carrier 34 to permit downward movement of thecarrier as will be more fully hereinafter set forth. A pair ofdiametrically opposed keys or lips 42 extend downwardly from the flange36 and are adapted to enter complementary grooves or slots 44 providedin the upper end 20 of the lower housing section 10 when the carrier 34has been moved to a down position as illustrated in Fig. 4.

A plurality of circumferentially spaced T-shaped grooves 46 (see Fig. 3)are provided in the upper outer surface of the carrier ilange 36 toreceive and support dog members 48. Oppositely extending studs 50 areprovided on the lower end of each of the dogs 48 and are adapted to berotatably disposed in the outer ends 52 of the respective T-shaped slot46. The dogs 48 thus may be pivoted with respect to the carrier flange36 as will hereinafter appear. A pair of spaced apertures 54 areprovided in the flange 36 at the lower end of each T-shaped slot 46 toreceive small helical springs 56. The springs 56 extend upwardly intothe respective slot 46 in contact with the lower end 58 of therespective dog 48. The lower end 58 of each dog 48 is tapered upwardlyand inwardly with respect to the carrier ange 36. Thus the force exertedby the helical springs 56 on the tapered ends 58 will yieldably retainthe dogs 48 in an inclined position as illustrated in Fig. l. The upperend 60 of each dog 48 is tapered in the same direction (Fig. 2) as theopposite lower end 58 thereof, and is provided with a series of teeth orserrations 62 (Figs. 2 and 3). The teeth 62 are provided to engage thelower end of a tool joint and are disposed at an oblique angle, i. e.,the teeth 62 are biased outwardly and upwardly (when viewed from the topthereof with the inner edge of the dog 48 to the left) for purposes aswill be hereinafter set forth.

Operation As previously set forth, a string of drill pipe is frequentlystuck in a well bore some distance above the bottom of the bore. Toremove the drill pipe, the overshot 2 is assembled in a string of washpipe 4 as illustrated in Fig. l. The carrier 34 is retained in its upperposition as shown in Fig. l by the stud 40, and heavy lubricant isprovided in the chamber 38 as heretofore set forth. The wash pipe 4 isthen lowered into the well bore (not shown) and telescoped downwardlyover the drill pipe 64 (shown in dotted lines in Fig. l and solid linesin Fig. 4). The wash pipe 4 is moved downwardly until a tool joint 66 isin the upper portion of the overshot 2 as shown in Fig. l, or a distanceabove the overshot 2 (not shown). It will be apparent that the innerdiameter of the carrier 34, as well as the remainder of the overshot 2,is suiicient to permit substantially free movement of the overshotdownwardly over the tool joint 66. Furthermore, the dogs 48 will pivotoutwardly against the action of the springs 56 when contacted by thetool joint 66 to permit downward movement of the overshot 2 over thetool joint.

When the overshot 2 is disposed over the drill pipe 64 as shown in Fig.l, fluid is circulated from the surface through the wash pipe 4 andovershot 2 to wash the stuck drill pipe 64 loose. As the drill pipe 64is washed loose and falls, the lower flat end of the tool joint 66 willengage the teeth 62 at the upper ends 60 of the dogs 48 as shown in Fig.4. The weight of the drill pipe 64 is then imposed through the medium ofthe tool joint 66 and dogs 48 to the movable carrier 34. This excessiveweight will move the carrier 34 downwardly in the bores 32 and 26 andfracture the retaining stud 40. Vertically spaced apertures 68 arepreferably provided in the walls of the carrier 34 to provide restrictedoutlets for the lubricant from the chamber 38. It will be apparent thatas the carrier 34 moves downwardly, the apertures 68 are successivelycut off by the upper end 20 of the lower housing section l0 to reducethe outlet area for the lubricant from the chamber 38. The reduction inthe outlet area for the lubricant provides an increasing uid pressureforce on the lower surface of the ange 36, thereby providing a dash potaction for the carrier 34 to gradually bring the carrier 34 and thedrill pipe 64 to a stop. The exhorbitant stresses which would resultfrom the sudden stopping of the falling drill pipe 64 are thus avoidedand the shock imposed on the overshot 2 and wash-over pipe 4 is reducedto a minimum. It will be noted that when the carrier 34 is moved to itsdown position, as illustrated in Fig. 4, the keys 42 are disposed in thecomplementary grooves 44.

The wash pipe 4 is then raised to raise the drill pipe 64 and remove itfrom the well bore. In the event the drill pipe v64 again becomes stuckduring upward movement of the wash pipe 4, and cannot be removed fromthe well bore, the wash pipe 4 is lowered to reduce the force imposed bythe dogs 48 on the tool joint 66. The wash pipe 4 is then rotatedclockwise to release the dogs 48 from the tool joint 66. Since the teeth62 are biased as heretofore set forth, the teeth 62 will react with thelower end of the tool joint 66 to pivot the dogs 48 outwardly out fromunder the tool joint 66. The wash pipe 4 and overshot 2 is maintained incontinuous rotation and raised through the well bore. lt will be notedthat the cooperating grooves 44 and keys 42 will cause rotation of thecarrier 34 simultaneously with the overshot 2.

In the event the drill pipe 64 becomes stuck again as set forth above,but before the studs 40 are broken or sheared, the wash pipe 4 may beraised to bring the dogs 48 into contact with the tool joint 66. Thelower surface of the ilange 36 will thereby be retained in contact withthe studs 40. The` wash pipe 4 and overshot 2 may then be rotatedclockwise, whereupon the studs 40 will contact the keys 42 to transmitthe rotation to the carrier 34 and dogs 48 to release the dogs as setforth above. The overshot 2 may then be removed from the well bore.

M odifed structure Referring to Fig. 5, reference character 70 generallydesignates a modified overshot for engaging tool joints having taperedends and also adapted to be interposed in a string of wash pipe (notshown). The overshot 70 comprises a cylindrical housing constructed inupper and lower sections 71 and 72 respectively. The upper end of thelower housing section 72 is secured to the lower end of the upperhousing section 71 by threads 73. The upper end (not shown) of the uppersection 71 and the lower end (not shown) of the lower section 72 are 5,adapted' to, be intero nneeted rto lthe wash pipe in the same manner asthe overshot 2 shown in Figs. 1- and' 4*.

A bore 74 extends longitudinally through the upper housing section 71 toreceive and permit passage of the drill pipe 75V therethrough. The bore74 is enlarged at 76 to provide a bore 77of greater diameter through thelower portion ofthe upper housing section 71. A bore 78 also extendslongitudinally through the lower housing section 72'- and-communicateswiththe bore 77. The bore 78 is smaller in diametery than the bore 77Ikfor purposes as will be hereinafter set forth.

A lower tubular shaped carrier member 79 is disposed in the lowerportionof the bore, 7,7y and extends downwardly into the bore 7-8. Themain body portion of the lower carrier 79 is of a size to provide aloose sliding fit thereof in the bore 78. A, circumferential flange 80is provided' on the upper end' of the lower carrier 79 and is of a sizeto provide asliding fit thereof in the bore 77. The inner periphery ofthe carrier 79 is tapered downwardly and inwardly atV the upper end 79athereof. The annular space or chamberl provided between the main bodyportion of the lower carrier 79vandthe walls of the bore 77, when thecarrier 79 is in the upper position as shown in Fig. is normallyllediwithrahydraulic uid and preferably aheavylubricant. The lowercarrier 79 is retained in its upper position by a pair of diametricallyopposed breakable studs 82- threadedly secured in theV side walls ofthehousing section 7lY and extending into the bore 77Y underneath the angeSi). These studs S2 are broken when a large downward force is-imposed onthe lower carrier 79 to permitdownwardmovement of the carrier as will behereinafter setrforth.

Anupper tubular shaped carrier 83 is disposed in the bore 77 above thelower carrier 79 and is of a size to move freelythroug-h the bore77 aswill be hereinafter setforth. A pairof diametricallyropposed arcuateslots 84 are provided in the upper end-l 85- of thev carrier 83 asis'clearly shown in Fig. 6. The slots 84'are adapted to receive a pairlof diametrically opposed locking studs 86 extending inwardly into thebore 77 above the carrier 33 tolock the car-rier 83 in anupper-'position (not shown) as will be hereinafter set forth.

A plurality of arcuate springs $7k are secured in complementary slots8S` in the upperY inner.v portion of the carrier 83` by suitable boltsor the like (notshown). The springs 871 are commonly. called. bellysprings and are adapted' toi engage the tool joint 89 uponv movement ofthetool joint downwardly through the overshot and'provide movement ofthe carrier 83A with the tool joint 89. The springs 8.7' maybecompressed by the tool joint 89 in the usual manner to permit movementof the tool joint S9 through the carrier SSLwhen the carrier is lockedin the overshot 7i) as` will bemore fully hereinafter set forth.

Circumferentially spaced friction shoes 90 are also provided in thecarrier S3. below the belly springs 87 to engage the tool joint 89. Eachof the friction shoes 90 is disposed in a complementary slot 91 providedin the wall ofthe carrier 83:.as shown in Fig. 7. Lips or flanges 92extend from the innerwall of the carrier 83 and overlie the oppositeends of each slot 91 to engage the upper and lower ends of the frictionshoe 90 and limit the inward movement of the shoe. A closure member 93is secured to the outer, wall of the carrier 83 by any suitable means(not shown) over eachof the slots. 91 to prevent drilling mud and thelike from entering the slots 91 and interferl ing with the operation ofthe friction shoes 90. A pair of small helical springs. )d` are providedin each slotI 91 and are anchored at their opposite ends to the closureplate 93 and the friction shoe 90. The springs 94 obviously continuouslyurge thek shoes 90 inwardly into the carrier 8 3 for engagement with thetool joint 89. Furthermore, the shoes 90 maybe moved. outwardly intheslots 91 upon contact with the tool joint 89 to permit passage offthetool joint through` the carrier 83, however, the shoes; 90.` will. tendto.drag` on thetoolE joint 89Y and (i tend to move the carrier 83 withthe tool joint. The friction shoes 90 and belly springs 87 perform thesaine function and may be interchanged at will. That is, either one orboth may be used.

A plurality of circumferentially spacedA slips 95 are secured to thelower end 96 of the ycarrier 83 and are adapted to enter the uppertapered end 79a of the lower carrier 79; The slips 95 extend intovcomplementary T- shaped slots 98 provided in the outer surface of thecarrier 83 at the lower end 96 thereof; Studs 99 extend from oppositesides of each slip 95` adjacent the upper end 160 thereof to pivotallysupport the slips 95 in the T-shaped slots 98. An aperture 101 isprovided in the wall of the carrier 83 at the upper end of each of theT-shaped slots 98 to receive a small helical spring 102. The springs 102extend downwardly and engage the upper end 100 of the complementary slip95,. The, upper end 100 of each slip 95 is tapered downwardly andoutwardly; therefore, the force imposed by the helicaly springs 102thereon tends to pivot the slips 95 on their supporting studs 99 andretain the slips 95 in an inclined position opposite to the positionillustrated in Fig. 5, for purposes as will be hereinafter set forth.

Operation To remove the stuck drill pipe 75 from a well bore (notshown), the overshot is interposed in a string of wash pipe with thecarriers 79 and 83 in the position. shown in Fig. 5, and with heavylubricant disposed in the chamber 81 around the lower carrier 7,9. Theover,- shot 70 is then lowered into the well borek and is tele; scopeddownwardly over the drill pipe until the tool joint 89 is in theposition above the upper carrier 83 as illustrated in Fig. 5. The innerdiameter of the lower carrier '79 is of sufficient size to permit freemovement of the tool joint 89 therethrough, and the lockingv studs 36will contact the upper end 85 of the upper carrier 83 to limit theupward movement of the carrier caused byengagement of the friction shoesand belly springs S7 with the tool joint 89. When the carrier 83isstopped in the housing 7l, the tool joint 89 will compress, thesprings 87 and move the friction shoesY 90 outwardly to permit movementof the carrier 83 downwardly over the tool joint with the housing 71.

Fluid is then circulated through the wash pipe and overshot 70 to loosenthe drill pipe 75 and cause the drill pipe to fall downwardly in thewell bore. As the tool joint 89 moves downwardly through thebore 7,7, itengages the belly springs 87 and friction shoes 90 yto move the uppercarrier S3 simultaneously downward. As the slips enter the upper taperedend 79a of the lower carrier 79, they are forced inwardly until theirlower ends are moved into contact with each other adjar,

cent the drill pipe 75 as shown in Fig. 5. The upper carrier 83 willthen be instantaneously stopped, whereupon the tool joint 89 will moveon downward through the carrier 83 until the lower tapered end 103thereof engages the slips 95. Atithis time, the weight of the fallingdrill pipe 75 is imposed through the tool joint 89 and slips 95 to thelower carrier 79, thereby forcing both carriers 79 and $3 downwardlysimultaneously with the drill pipe 75.

The studs 82 will bel broken during` the initial down-` ward movement ofthe lower carrier 79-asyheretofore set forth. As the lower carrier 79 ismoved downwardl in the bore 77, the heavy lubricant contained inl theannular chamber 81 will be ldischarged through the small annular opening(not shown) provided between the outer surface of they carrier 79 andthe wallsv of the lower bore 78. It will be apparent that this outletfor the fluid will be limited to provide a iiuid pressure force on thelower area of the flange 80, thereby decreasing the speed of thedownwardly moving drill pipe 75. Furthermore, the further the lowercarrier 79 enters the bore 78, the more friction will beprovidedv torestrict the discharge of the lubricant. Thus, the pressure forceexerted by the lubricant in chamber 81 on the lower area of the flange80Vwill be substantially constantly increased to gradually decrease thespeed of the drill pipe 75. The carrier 79 is stopped upon contact ofthe flange 80 with the upper end of the lower housing section 72. Inthis manner, the drill pipe is gradually brought to rest to provide aminimum strain on the overshot 70 and the interconnected wash pipe. Itwill be understood that vertically spaced apertures (not shown) may beprovided in the walls of the lower carrier 79 to form outlets for thelubricant from the chamber Si in conjunction with, or in the place of,the outlet formed by the annulus between the outer surface of thecarrier 79 and the walls of the lower bore 78.

The overshot 70 may then be raised to remove the drill pipe 75 from thewell bore. ln the event the drill pipe 75 again becomes stuck, theovershot 70 is lowered to bring the locking studs 86 into contact withthe upper end 85 of the upper carrier member 83. During the downwardmovement of the overshot 70, the belly springs 87 and friction shoes 90will engage the tool joint 89 to retain the upper carrier 83 in a fixedposition and permit movement of the housing section 7l thereover.However, the lower carrier 79 will move downwardly simultaneous with thehousing section 7i by virtue of friction between the flange 8i) and thebore 77 as well as gravity to remove the slips 9S from the taperedsection 79u. As the studs 86 contact the upper end of the carrier 83,the housing section 7l is continued moved in a downward direction and issimulatneously rotated counterclockwise. However, the springs 87 andshoes 94) contacting the tool joint 89 will restrain rotation of thecarrier 83. Thus, the studs S6 are moved into the slots S4 into aposition underneath the overhanging lips 165. The overshot 70 may thenbe raised and removed from the well bore over the drill pipe 75. Sincethe upper carrier 83 is then in spaced relation to the lower carrier 79,the slips 95 will be sprung outwardly by the action of the helicalsprings 102 to preclude contact of the slips with the tool joint 39, orother tool joints (not shown) above the tool joint 89, and permit freeupward movement of the carrier section 83 with the housing 7l.

From the foregoing, it is apparent that the present invention provides anovel overshot adapted to be interposed in a string of wash pipe wherebythe number of trips into a well bore for the removal of stuck drill pipewill be reduced to a minimum. The overshot catches the drill pipe uponits being washed loose in the well bore to preclude the necessity ofagain lishing for the drill pipe. Each embodiment of the overshotutilizes a movable carrier having means to engage the tool joint. Thecarrier, in each embodiment, has a circumferential ange providing adownwardly facing pressure area on which is applied an increasing fluidpressure force dur ing downward movement of the carrier to graduallystop the downward movement of the falling drill pipe and reduce thestrain on the wash pipe to a minimum. Furthermore, the overshot may bereadily disengaged from the drill pipe in the event it cannot be removedfrom the well bore to permit removal of the overshot and wash pipe.

Changes may be made in the combination and arrangement of parts asheretofore set forth in the specification and shown in the drawings, itbeing understood that any modification in the precise embodiment of theinvention may be made within the scope of the following claims withoutdeparting from the spirit of the invention.

I claim:

l. An overshot adapted to be telescoped over a string of drill pipehaving a tool joint interposed therein, coinprising a tubular housing,tubular carrier means reciprocally disposed in the housing, breakablelugs in the housing engaging the carrier means to normally retainjthecarrier means in one position in the housing, an outwardly extendingcircumferential ange on the carrier means, an inwardly extendingcircumferential flange on the housing providing a chamber between saidflanges for hydraulic fluid, means carried by the carrier means toengage the drill pipe tool joint upon movement of the tool jointdownwardly through the housing, and restricted outlet means for saidhydraulic fluid to control the downward movement of the carrier.

2. An overshot adapted to be telescoped over a string of drill pipehaving a tool joint interposed therein, comprising a tubular housing,tubular carrier means reciprocally disposed in the housing, stop meansin the housing to limit the downward movement of the carrier means,means normally retaining the carrier means in spaced relation to saidstop means, means carried by the carrier means to engage the drill pipetool joint upon movement of the tool joint downwardly through thehousing, a downwardly facing pressure area on said carrier means, andmeans for maintaining a hydraulic uid pressure on said area to controlthe downward movement of the carrier upon engagement thereof with thetool joint.

3. An overshot adapted to be telescoped over a string of drill pipehaving a tool joint interposed therein, cornprising a housing having abore extending therethrough, said bore having an upper large diameterportion and a lower small diameter portion, a tubular shaped carrierreciprocally disposed in the small diameter portion of said bore andextending upwardly into the larger diameter portion of said bore, acircumferential flange on the upper end of the carrier of a size toprovide a sliding fit thereof in the larger diameter portion of thebore, breakable means in the housing for retaining the carrier in anupper position in the housing, a body of lubricant in the largerdiameter portion of the bore under said circumferential liange to resistdownward movement of the carrier, restricted outlets for the lubricant,and means on the carrier to engage the drill pipe tool joint upondownward movement of the tool joint through the housing.

4. An overshot adapted to be telescoped over a string of drill pipehaving a tool joint interposed therein, comprising a tubular housing, atubular carrier reciprocally disposed in the housing, dogs pivotallysupported on the carrier, means constantly urging the dogs to a positionextending inwardly into the carrier, whereby the dogs will engage thedrill pipe tool joint upon movement of the tool joint downwardly throughthe housing and impose the weight of the tool joint on the carrier,means on the carrier providing a downwardly facing pressure area, andmeans for maintaining a fluid pressure force on said pressure area tocontrol the downward movement of the carrier and tool joint.

5. An overshot adapted to be telescoped over a string of drill pipehaving a tool joint interposed therein, comprising a tubular housing, atubular carrier reciprocally disposed in the housing, dogs pivotallysupported on the carrier, means constantly urging the dogs to a positionextending inwardly into the carrier, whereby the dogs will engage thedrill pipe tool joint upon movement of the tool joint downwardly throughthe housing and impose the weight of the tool joint on the carrier, acircumferential flange on the carrier, a coniining chamber underneathsaid flange for the reception of uid, and means to control the dischargeof fluid from the chamber to control the downward movement of thecarrier and tool joint.

6. An overshot adapted to be telescoped over a string of drill pipehaving a tool joint interposed therein, comprising a tubular housing, atubular carrier reciprocally disposed in the housing, dogs pivotallysecured to the upper end of the carrier, spring means in the carrierconstantly urging the dogs in a tilted position extending inwardly andupwardly into the carrier, whereby thc dogs will engage the lower end ofthe drill pipe tool joint upon downward movement of the tool jointthrough the housing to impose the weight of the drill pipe on thecarrier, means providing for hydraulic control of the downward movementof the carrier to gradually stop the downward movement of the drillpipe, and teeth on the upper ends of the dogs, said teeth being formedon a bias whereby upon rotation of the carrier in one direction theteeth react on the tool joint to pivot the dogs outwardly from under thetool joint.

7. An overshot adapted to bev telescoped over a string of drill pipehaving a tool joint interposed therein, cornprising a tubular housing, atubular carrier reciprocally disposed in the housing, dogs pivotallysecured to the upper end of the carrier, spring means in the carrierconstantly urging the dogs in a tilted position extending inwardly andupwardly into the carrier, whereby the dogs will engage the lower end ofthe drill pipe tool joint upon downward movement of the tool jointthrough the housing to impose the weight of the drill pipe on thecarrier, means providing for hydraulic control of the downward movementof the carrier to gradually stop the downward movement of the drillpipe, teeth on the upper ends of the dogs, said teeth being formed on abias whereby upon rotation of the carrier in one direction the teethreact on the tool joint to pivot the dogs outwardly from under the tooljoint, keys on the carrier, and complementary slots in the housing toreceive the keys when the carrier is in a down position, wherebyrotative movement of the housing will be imparted to the carrier.

8. An overshot adapted to be telescoped over a string of drill pipehaving a tool joint interposed therein, comprising a tubular housing, atubular carrier reciprocally disposed in the housing, dogs pivotallysecured to the upper end of the carrier, spring means in the carrierconstantly urging the dogs in a tilted position extending inwardly andupwardly into the carrier, whereby the dogs will engage the lower end ofthe drill pipe tool joint upon downward movement of the tool jointthrough the housing to impose the weight of the dn'll pipe on thecarrier, a downwardly facing pressure area on the carrier providing anannulus between the housing and the carrier, a body of fluid confined insaid annulus, means for controlling the discharge of the uid togradually stop the downward movement of the carrier and drill pipe,teeth on the upper ends of the dogs, said teeth being formed on a biaswhereby upon rotation 'of the carrier in one direction the teeth reacton the tool joint to pivot the dogs outwardly from under the tool joint,keys on the carrier, and complementary slots in the housing to receivethe keys when the carrier is in a down position, whereby rotativemovement of the housing will be imparted to the carrier.

9. An overshot adapted to be telescoped over a string of drill pipehaving a tool joint interposed therein, comprising a tubular housing,tubular carrier means reciprocally disposed in the housing, acircumferential flange on the outer surface of the carrier meansproviding an annulus between the housing and carrier means below theflange, hydraulic fluid in the annulus, means carried by the carriermeans to engage the drill pipe tool joint upon movement of the tooljoint downwardly through the housing, said carrier provided withrestricted outlet means for the hydraulic iuid to control the downwardmovement of the carrier means, and stopfmeans in the housing to limitthe downward movement of the carrier.

References Cited in the tile of this patent UNITED STATES PATENTS1,411,546 Winger Apr. 4, 1922 1,471,775 Brown Oct. 23, 1923 1,494,135Robinson et al May 13, 1924 2,026,295 Baker Dec. 31, 1935 2,508,285 Otiset al Mayk 16, 1950 2,519,288 Roberson Aug. l5, 1950 2,605,131 Marshallet al July 29, 1952 2,619,374 Davidson Nov. 25, 1952

